微服务就是将项目的各个模块拆分为可独立运行、部署、测试的架构设计风格。而在SpringCloud中要实现微服务的架构,就离不开Eureka的使用.Eureka就相当于是zookeeper的一个注册中心,负责管理server和client的连接. Eureka 是 Netflix 公司开源的一个服务注册与发现的组件 。 • Eureka 包含两个组件：Eureka Server (注册中心) 和 Eureka Client (服务提供者、服务消费者)。
创建module -父工程 Spring-cloud-parent Spring-cloud-parent pom.xml
<!--spring boot 环境 --> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.0.RELEASE</version> <relativePath/> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties>创建服务提供者eureka-provider eureka-provider pom.xml
<dependencies> <!--spring boot web--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> </dependencies>GoodsController
package com.itheima.provider.controller; import com.itheima.provider.domain.Goods; import com.itheima.provider.service.GoodsService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * Goods Controller 服务提供方 */ @RestController @RequestMapping("/goods") public class GoodsController { @Autowired private GoodsService goodsService; @GetMapping("/findOne/{id}") public Goods findOne(@PathVariable("id") int id){ Goods goods = goodsService.findOne(id); return goods; } }GoodsService
package com.itheima.provider.service; import com.itheima.provider.dao.GoodsDao; import com.itheima.provider.domain.Goods; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; /** * Goods 业务层 */ @Service public class GoodsService { @Autowired private GoodsDao goodsDao; /** * 根据id查询 * @param id * @return */ public Goods findOne(int id){ return goodsDao.findOne(id); } }Goods
package com.itheima.provider.domain; /** * 商品实体类 */ public class Goods { private int id; private String title;//商品标题 private double price;//商品价格 private int count;//商品库存 public Goods() { } public Goods(int id, String title, double price, int count) { this.id = id; this.title = title; this.price = price; this.count = count; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getCount() { return count; } public void setCount(int count) { this.count = count; } }GoodsDao
package com.itheima.provider.dao; import com.itheima.provider.domain.Goods; import org.springframework.stereotype.Repository; import javax.validation.ReportAsSingleViolation; /** * 商品Dao */ @Repository public class GoodsDao { public Goods findOne(int id){ return new Goods(1,"华为手机",3999,10000); } }ProviderApp
package com.itheima.provider; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; /** * 启动类 */ @SpringBootApplication public class ProviderApp { public static void main(String[] args) { SpringApplication.run(ProviderApp.class,args); } }application.yml
server: port: 8000Goods
package com.itheima.consumer.domain; /** * 商品实体类 */ public class Goods { private int id; private String title;//商品标题 private double price;//商品价格 private int count;//商品库存 public Goods() { } public Goods(int id, String title, double price, int count) { this.id = id; this.title = title; this.price = price; this.count = count; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getCount() { return count; } public void setCount(int count) { this.count = count; } }ConsumerApp
package com.itheima.consumer; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class ConsumerApp { public static void main(String[] args) { SpringApplication.run(ConsumerApp.class,args); } }application.yml
server: port: 9000• Spring提供的一种简单便捷的模板类，用于在 java 代码里访问 restful 服务。 • 其功能与 HttpClient 类似，但是 RestTemplate 实现更优雅，使用更方便。
修改消费方代码
RestTemplateConfig
package com.itheima.consumer.config; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.client.RestTemplate; @Configuration public class RestTemplateConfig { @Bean public RestTemplate restTemplate(){ return new RestTemplate(); } }OrderController
package com.itheima.consumer.controller; import com.itheima.consumer.domain.Goods; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate; /** * 服务的调用方 */ @RestController @RequestMapping("/order") public class OrderController { @Autowired private RestTemplate restTemplate; @GetMapping("/goods/{id}") public Goods findGoodsById(@PathVariable("id") int id){ System.out.println("findGoodsById..."+id); /* //远程调用Goods服务中的findOne接口 使用RestTemplate 1. 定义Bean restTemplate 2. 注入Bean 3. 调用方法 */ String url = "http://localhost:8000/goods/findOne/"+id; // 3. 调用方法 Goods goods = restTemplate.getForObject(url, Goods.class); return goods; } }但是此种方式调用路径被写死,必须调用指定路径的工程才能够实现,所以我们要修改成为能够动态获取所有provider路径,这里我们就要使用Eureka.
① 创建 eureka-server 模块
② 引入 SpringCloud 和 euraka-server 相关依赖
Spring-cloud-parent pom.xml
<properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> <!--spring cloud 版本--> <spring-cloud.version>Greenwich.RELEASE</spring-cloud.version> </properties> <!--引入Spring Cloud 依赖--> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>${spring-cloud.version}</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement>eureka-server pom.xml
<dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- eureka-server --> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency> </dependencies>EurekaApp
package com.itheima.eureka; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer; @SpringBootApplication // 启用EurekaServer @EnableEurekaServer public class EurekaApp { public static void main(String[] args) { SpringApplication.run(EurekaApp.class,args); } }③ 完成 Eureka Server 相关配置
application.yml
server: port: 8761 # eureka 配置 # eureka 一共有4部分 配置 # 1. dashboard:eureka的web控制台配置 # 2. server:eureka的服务端配置 # 3. client:eureka的客户端配置 # 4. instance:eureka的实例配置 eureka: instance: hostname: localhost # 主机名 client: service-url: defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka # eureka服务端地址，将来客户端使用该地址和eureka进行通信 register-with-eureka: false # 是否将自己的路径 注册到eureka上。eureka server 不需要的，eureka provider client 需要 fetch-registry: false # 是否需要从eureka中抓取路径。eureka server 不需要的，eureka consumer client 需要④ 启动该模块
① 引 eureka-client 相关依赖
eureka-provider pom.xml
<dependencies> <!--spring boot web--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- eureka-client --> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> </dependency> </dependencies>ProviderApp
package com.itheima.provider; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; /** * 启动类 */ @EnableEurekaClient //该注解 在新版本中可以省略 @SpringBootApplication public class ProviderApp { public static void main(String[] args) { SpringApplication.run(ProviderApp.class,args); } }② 完成 eureka client 相关配置
application.yml
server: port: 8001 eureka: instance: hostname: localhost # 主机名 client: service-url: defaultZone: http://localhost:8761/eureka # eureka服务端地址，将来客户端使用该地址和eureka进行通信 spring: application: name: eureka-provider # 设置当前应用的名称。将来会在eureka中Application显示。将来需要使用该名称来获取路径③ 启动 测试
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服务消费者eureka-consumer通过修改，也可以展示在控制台
eureka-consumer在这里仅仅是我们人为定义为消费者，作为一个服务，其实既可以作为服务提供方，同时也可以作为服务消费方
ConsumerApp添加@EnableEurekaClient
package com.itheima.consumer; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; @EnableEurekaClient @SpringBootApplication public class ConsumerApp { public static void main(String[] args) { SpringApplication.run(ConsumerApp.class,args); } }application.yml
server: port: 9000 eureka: instance: hostname: localhost # 主机名 client: service-url: defaultZone: http://localhost:8761/eureka # eureka服务端地址，将来客户端使用该地址和eureka进行通信 spring: application: name: eureka-consumer # 设置当前应用的名称。将来会在eureka中Application显示。将来需要使用该名称来获取路径需要导入DiscoveryClient,从而获取到配置文件中的ip和端口号 ConsumerApp添加@EnableDiscoveryClient
package com.itheima.consumer; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; @EnableDiscoveryClient // 激活DiscoveryClient @EnableEurekaClient @SpringBootApplication public class ConsumerApp { public static void main(String[] args) { SpringApplication.run(ConsumerApp.class,args); } }OrderController修改代码动态获取路径
package com.itheima.consumer.controller; import com.itheima.consumer.domain.Goods; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.cloud.client.ServiceInstance; import org.springframework.cloud.client.discovery.DiscoveryClient; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate; import java.util.List; /** * 服务的调用方 */ @RestController @RequestMapping("/order") public class OrderController { @Autowired private RestTemplate restTemplate; @Autowired private DiscoveryClient discoveryClient; @GetMapping("/goods/{id}") public Goods findGoodsById(@PathVariable("id") int id){ System.out.println("findGoodsById..."+id); /* //远程调用Goods服务中的findOne接口 使用RestTemplate 1. 定义Bean restTemplate 2. 注入Bean 3. 调用方法 */ /* 动态从Eureka Server 中获取 provider 的 ip 和端口 1. 注入 DiscoveryClient 对象.激活 2. 调用方法 */ //演示discoveryClient 使用 List<ServiceInstance> instances = discoveryClient.getInstances("EUREKA-PROVIDER"); //判断集合是否有数据 if(instances == null || instances.size() == 0){ //集合没有数据 return null; } ServiceInstance instance = instances.get(0); String host = instance.getHost();//获取ip int port = instance.getPort();//获取端口 System.out.println(host); System.out.println(port); String url = "http://"+host+":"+port+"/goods/findOne/"+id; // 3. 调用方法 Goods goods = restTemplate.getForObject(url, Goods.class); return goods; } }当我们使用Dubbo时,使用zookeeper作为我们的注册中心,但是为了防止注册中心宕机,我们通常配置多个zk作为集群,来同时对消费者和提供者提供服务.但是zk作为集群,会有一个较大的问题. zk集群的三种情况进行leader选举:
zk启动时半数的flower挂掉时,需要重新选举leader挂掉时我们都知道zk集群在面对三种情况时,会重新进行leader选举,而由于zk为了保持一致性和分区容错性,就会牺牲一部分的可用性. 当重新进行leader选举的时候整个zk集群都会停止对外提供服务,直到新的leader选举出来之后才会重新对外提供服务,而通常一次选举在30s-90s之间,而这一段时间都处于宕机状态,这对于一些项目来说是不可容忍的.所以面对这种情况,Eureka的设计时不同于zk. 在Eureka的集群中,我们通常主要保证集群的高可用性和分区容错性,牺牲一部分的一致性.在Eureka集群中没有Leader和Flower之分,每一个节点都是平等的,并且在Eureka中存在自我保护机制(即使这个节点有问题,但是依然处于集群中,不会断掉).从而保证即使一个节点宕机,但是整个集群依然对外提供服务,只是可能会产生部分数据丢失.
